Apparatus for balancing rotatable bodies



P 1936- B. E. OHLSON 2,054,267

APPARATUS FOR BALANCING ROTATABLE BODIES Filed April 14, 1933 5Sheets-Sheet l INVENTOR ATTORNEY Sept. 15, 1936. E, QHLSON 2,054,267

APPARATUS FOR BALANCING ROTATABLE BODI-ES Filed April 14, 1933 5Sheets-Sheet 2 INVENT OR BY I 7MK ATTORNEY Sept. 15, 1936. QHLSQN2,054,267

APPARATUS FOR BALANCING ROTA'I'ABLE BODIES Filed April 14, 1933 5SheetsSheet 3 INVENTOR BY v ATTORNEY Sept. 15, 1936; B, E, HL 2,054,267

APPARATUS FOR BALANCING ROTATABLE BODIES Sept. 15, 1936. E QHLSON2,054,267

APPARATUS FOR BALANCING ROTATA BLE BODIES Filed Aprii 14, 1933 5Sheets-Sheet 5 INVENTOR A TTORNE Y Patented Sept. 15,1936

UNITED STATES APPARATUS FOR B Bengt Erik ohlson, Philadelphia, Pa...

ALANCING BOTAT a DIE assignor to Tinius Olsen Testing Machine Company,Philadelphia, Pa., a corporation oi Pennsylvania ApplioationAprll 14,1e33, Serial No. 866,085

' 11 Claims. (Cl. 13-51) The object of this invention is to devise anovel apparatus for balancing rotatable bodies wherein the vibration dueto unbalance is converted into electrical energy. The amount ofunbalance is visibly indicated on an electric meter, and the angle ofunbalance is visibly indicated on an angle indicator.

In carrying out my novel method, the amount of unbalance is determinedby measuring the induced current created by relative movement, due ,tounbalance of the body being tested, of a magnet and solenoids.

The amount of unbalance is determined by the amplitude of a vibratoryframe on which the body is revolving. The purpose of varying the naturalperiod of vibration is to accommodate the machine for bodies 01'different weights, or for equalizing the vibrations at each end so thatthe register of unbalance can be read on the same scale.

The balancing machine is run at a constant speed and the angle andamount of unbalance may be taken at a period of vibrationeither above,in, or below the critical speed, provision being made for changing thenatural period of vibration of the vibratory system while the drivingmotor is running at a constant speed.

With the above and other objects in view, as

' will hereinafter fully be set forth my invention 30 comprehends anovel apparatus for balancing rotatable bodies.

It further comprehends a novel method of and apparatus for balancingwherein the vibrations due to unbalance are converted into elec tricalenergy and the amount of unbalance visibly indicated on a meter.

It further comprehends a novel apparatus for balancing wherein thevibrations due to unbalance are utilized to induce a current by causingrelative movement between a magnet and solenoids, and measuring suchinduced current to determine the amount of unbalance.

It further comprehends novel means for changing the natural period ofvibration while the 45 machine is running.

It further comprehends a novel apparatus for.

determining the angle of unbalance of a rotatable body by relativeadjustment of the position of brushes to a commutator driven at the samespeed 5 as the body to be balanced or at a fixed relative speed. I Othernovel features of construction and advantage will hereinafter appear inthe detailed description and the appended claims. 5 For the purpose ofillustrating the invention, I

have shown in the accompanying drawings a typical embodiment of it,which, in practice, will give satisfactory and reliable results. It is,however, to be understood that this embodiment is typical only and thatthe various instrumentalities of which my invention consists can bevariously arranged and organized, and the invention is not limited tothe precise arrangement and organization of these instrumentalities asherein set forth.

Figure 1 is a top plan view of a balancing machine embodying myinvention.

Figure 2 is a side elevation of the balancing machine.

Figure 3 is an end elevation of the balancing machine. I

Figure 4 is a sectional plan view showing more particularly thevibratory rods and the manner in which they are adjusted to vary theperiods of vibration.

Figure 5 is a sectional detail showing the manner of locking thevibratory frame.

Figure 6 is an end elevation oi a calibrating drive member.

Figure 7 is a side elevation of the angle indicating mechanism.

Figure 8 is an end elevation showing the brush arrangement of thecommutator.

Figure 9 is a side elevation, partly in section of the commutatormechanism.

Figure 10 is a sectional elevation of one of the commutatcrs.

Figure 11 is an end elevation of the commutator seen in Figure 10.

Figure 12 is a wiring diagram.

Referring to the drawings:

The base 3 has opening through its upper face inverted T shaped guideslots 4. Standards 5 are longitudinally adjustable on the base and areprovided with base plates which are fixed in the positions to which theyhave been adjusted by set screws 6 which engage T shaped shoes 1slidable in the guide slots 4. The standards 5 are chambered to providefor the free and unobstructed vibration of flexible rods 8. These rodsare rounded at their lower ends and are rotatably mounted in the baseplates of the standard. The rods are arranged in sets, each setconsisting of a pair of rods. Each rod of a set has mounted on it a wormgear 9 one of which has its teeth directed in a right hand direction,while the other gear of such set has its teeth directed in a left handdirection. The front and rear worm gears of a set mesh with a worm shaftIll provided with an actuating handle I I so that by turning the shaftill the natural period of vibration of the rods of a set may be varied.A spring i2 has its free ends bearing down upon the worm gears of a setand this spring is secured to its standard by a fastening device l8. Therods are thinned down inter- 5 mediate their ends to render them moreflexible and have the form of flat bands as shown at H,

see Figure 4. The vibration rods 8 have secured to their upper ends therods l5 which are more flexible than the rods 8, and these rods |5 arerota- 10 tably secured to a vibratory cradle or frame l8 consisting ofinterconnected side bars and cross bars by means of adjustable bracketsI 1.

In order to provide a right or left hand pivot for the vibratorymovement of the frame l8, each' standard 5 has journalled in it amanually actuated shaft |8 having a pinion |8 which meshes with a rack28 which carries a plunger 2| adapted to engage the inner race of a ballbearing 22 the outer race of which is fixed in a cross bar H of thevibratory frame l5, see more particularly Figure 5.

The base also has slidably mounted on it in the guide slots 4, endstandards 23 which are fixed in their adjusted position by means ofsuitable fastening devices 24 in a similar manner to that 5 in which thestandards 5 are fixed in their adjusted positions. Each standard 23 hasmounted on it at its upper end a pair of solenoids 25 with whichcooperate the armatures 26 in the form .of permanent magnets which arefixed to the vibra- 30 tory frame IS in any desired manner so thatanalternating electric current will be created by the vibratory movementof the stationary frame.

The vibratory frame 8, see Figure 3, is provided with sets of rollers 21mounted in brackets 28 5 which are adjustable longitudinally of theframe. The brackets are slidably mounted on the frame and provided withsuitable locking devices to retain them in the positions to which theyhave been adjusted. The rotatable body or specimen 40 to be tested 28has its shaft mounted on the rollers 21. 38 designates a spring, one endof which is fixed relatively to a bracket at the upper end of a standard23 and at its free end it is provided with a bracket 3| in which isjoumalled a roll 82.

The purpose of the spring mounted rolls 32 is to prevent relative upwardmovement of the shaft of the rotatable body with respect to the rollers21 during the revolution of the rotatable body. The machine is driven bymeans of an electric motor 38 mounted on the base and provided with apulley 34. around which passes a belt 35 which also passes around apulley 36, the shaft of which is connected with a drive shaft 31 havingtwo universais 38, and the outer section of this shaft 81 is journalledin a bearing 44 fixed to the vibratory frame. The shaft 31 at its freeend is provided with a driving member 48 having the pins 4| which enteropenings in a flanged collar 42 which has a friction fit on the shaft ofthe rotatable body 28.

The driving member 48 is mounted on the section 48 of the drive shaft 81and this shaft section is mounted in a journal bracket 44 fixed to the'vibratory support l8. The driving member 48 is in the form.of acalibrated disc which has two tapped holes 45, diametrically oppositeeach other and at the same radius from the centre of rotation. A screw46 of known weight-is fixed in one of these holes and the disc isbalanced with the 0 screw in fixed position. By removing this screw,

an unbalance is created equal to the weight of the screw times itsradius of rotation, and by fixing the screw in the other tapped hole 45,180 opposite, an unbalance of twice such value is made.

By means of these known quantities of unthe brush 55.

balance, the electric meter, which will be hereinafter explained, can beeasily calibrated.

The drive shaft 31 has a gear 48 fixed to it and this gear meshes with agear 41 on a shaft 48 mounted on a bracket 48. The shaft 48 drives a 5commutator having an insulating collar 58 which carries two conductingrings 5| and 52. The ring 5| is electrically connected with a segment58, and the ring 52 is electrically connected with a segment 54. Each ofthese segments are substan- 1 tially 180 apart except for the necessaryinsulation between them. A brush 55 contacts with the ring 5|, and abrush 58 contacts with the conducting ring 52.

51 designates a commutator shaft mounted 15 in the bracket 48 and inthreaded engagement with a brush holder 58' of insulating material.

The holder 58 has two sets of brush carriers, each set consisting of twobrushes spaced 180 apart, and with the brushes of one set spaced 29 90from the brushes of the other set. One set consists of the conductingposts 58 and 68 having the brushes 8| and 82 respectively. The otherconducting posts 63 and 84 have respectively the brushes 65 and 86.These brushes ride 25 on the semi-circular segments 53 and 54, whichlatter are retained in position on insulated hub 58 by screws Ill andheld on driving spindle 48 by the insulated washer 81 and the fasteningdevice 88. I The holder 58 has spaced conducting rings 68 and 18. e

The conducting post 58 is connected by a conductor 1| with a contact 12.The conducting post 68 is connected by a conductor 18 with a 35 contact14. The conducting post 68 is connected by a. conductor 15 with acontact 16, and the conducting post 64 is connected by a conductor 11with a. contact 18. The brush holder 58 has secured to it a springcontact 18 normally en- 40 gaging the contact 16 and connected bya'conductor with the conducting ring 68. The brush holder 58 has alsosecured to it a spring contact 8| normally engaging the contact 18 andconnected by a conductor 82 with the conductor 45 ring 18. The switchformed by the contacts 12 and 14, the contacts 16 and 18, and the springcontacts 18 and 8| is controlled by a push rod 88 of insulating materialand has its free end slotted or recessed so that it can pass by the con-50 tacts 18 and 18 and move the switch members formed by the springcontacts 18 and 8| out of engagement with such contacts 16-and 18 andinto engagement with the contacts 12 and 14.

The rod 83 passes through an angle indicat- 5 ing disc 84 graduated indegrees and extends into the brush holder 58. 85 is a stationarypointer, see Figure 1. vA brush 88 cooperates with the conducting ring68 and a brush 81 cooperates with the ring 18. The driving shaft 81 hasfixed 30- to it an angle indicating disc 88.

Referring now to the wiring diagram in Figure 12, the solenoids 25 havea common lead 88 lead-' ing to the brush 55. The solenoids 25 at theleft hand end have a line 88 leading to a contact 35 8| of a doublethrow switch |88 having a contact 8| paired with the contact 8| andhaving a contact 82 paired with a contact I83, the latter beingconnected by line I84 with the solenoids at the right hand end of themachine. The contacts MI and I82 are connected by line 85 with The brush88 is connected by line I86 with one terminal 'of a direct current meterI81, and the other terminal of said meter is connected by line m withthe brush :1.

access? The universal joint drive for the body to be tested is alwaysproperly aligned as one section of the drive shaft is iournalled on thevibratory support which is free to vibrate. III is the switch for themotor 38 and is mounted on a table I. The body to be balanced is placedon the bearings of the vibratory support and driven by support, and theother shaft is is actuated to unlock the other pivot, so that one end ofthe vibratory support is free to vibrate.

If the body is .out ofbalance at any point except in the plane of itspivot, such unbalance will cause a forced vibration of the supporthaving the same frequency as the revolutions per minute at which thebody is' revolved.

The vibrations of the support and the magnets 2! generate an alternatingelectromotive force, the magnitude of which is in proportion to theamplitude of vibration, and the phase relation to the driving spindlewill be dependent on the angular location of the unbalance. Thealternating current is integrated;

By adjusting by rotation of the disk as the brushes which are in contactwith the commutator until the commutator changes the direction of thecurrent just when the electromotive force is zero, the D. C. meterconnected with the.

brushes will indicate a maximum deflection. On account of the smallvalue of the electromotive force at this point, a-substantial change ofbrush position will result in a relatively small change of the meterhand deflection and thus the angular position of the brushes is not verydefinite.

If the other pair of brushes which are displaced from the first pair areconnected with the meter by pushing inwardly the push rod 83 of theswitch, the meter should read zero as the commutator splits up the A. C.cycle into two halves which counteract each other on the D. C. meter. Asthis second set of brushes will change the direction of the current whenthe electromotive force generated in the coils is maximum, a slightchange in the position of such brushes will result in a largerdeflection of the meter hand than the same change of the other pair ofbrushes. It will thus be seen that by utilizing the 90 displaced brushesa very accurate and definite position of the brushes can be determinedand also the phase angle of the A. C. current generated which dependsupon the angular positlon of the unbalance.

The angle of unbalance is read on the graduated angle indicator disc 84and after stopping the machine is referred to the body being balanced bymeans of the graduated disc 88 fixed to the driving shaft 31, so thatthe angle of unbalance can be accurately marked on the body for,cor-

rection.

The magnitude of unbalance is in direct proportion to the maximumreading on the D. C. meter. The meter can thus be calibrated to readounce inches of unbalance by determining the reading for one knownquantity of unbalance on the vibratory support.

The calibration can be readily accomplished by use of the balancedcalibrating disc 40 on the shaft 31. The screw at is of known weight,and, when removed from the hole 45 in which it was fixed when the discwas balanced, an unbalance equal to the weight of the screw timesits'radius of rotation is created. If the screw is fixed in the By meansof these known quantities of unbalance the meter can be easilyvcalibrated.

The amount of unbalance in the specimen is determined in a novel mannersince its value is determined by the amplitude of the movement of thevibratory frame which is in a direct proportion to the magnitude ofunbalance. This movement of the frame actuates the magnet 2' as amovable core in the two stationary coils 28. It is immaterial whetherthe coils are carried by the frame or the magnet, it simply beingnecessary to obtain relative movement between the magnet and the coils,as is apparent.

The electrical current induced in the coils by the vibratory movement ofthe frame is registered on the electric meter I01. This current variesaccording to theamplitude and movement of the vibratory frame It whichin turn is dependent on the amount of unbalance in the rotatable body.The current registered on themeter for a selected plane of correction istherefore varying according to the amount of unbalance in the body beingtested for unbalance.

Through the entire balancing operation the machine is run at a constantspeed and the natural periods of vibration of the balancing frame arevaried by mechanical means incorporated in the machine. The rods have adifferent degree of resistance and different resiliency in variousangular directions and by turning the rods in different angularpositions, various critical periods of vibration may be obtained. Theturning of the rods is accomplished by the hand levers H at each end ofthe machine while the machine is running and varies the amplitude ofvibration.

The handle II that operates the rods at the 1 opposite hole ll the valueof unbalance is doubled.

on the electric meter indicating the amount of unbalance at the end ofthe body which is being tested. For consistent and reliable unbalancereadings it is desirable to adjust the natural period of vibration sofar from the resonant or critical period either above or below, that theeffect of small speed variations of the driving motor is negligible.When it is desired to indicate infinitely small quantities ofunbalancethe machine may be adjusted to the resonant or critical period.

Referring now to the wiring diagram seen in Figure 12, when the lefthand end of the body is to be tested for unbalance the switch I00 ismoved to the left to engage contacts SI and till. Line 89 from coils 25at the left hand end of the machine leads to brush 55. conducting ring5| and commutator segment, 53 or 54. Line 90 leads from the same coilsthrough contact 8| switch lever Hi0, and line 905 to brush 58, ring 52and commutator segment 54 or 53.

When the switch arm I00 is moved toward the right, the coils 25 at theright end are connected by line 89 with brush 55, ring 5!, andcommutator segment 53 or 54, and by line I04, contact I03, contactarmI00, contact 602, line I05, brush 5B, and ring 52 with commutatorsegment 54 or 53.

The switch members 39 and 8| are normally in contact with contacts 56and 18 but when the switch rod 83 is pushed inwardly they move intoengagement with contacts 12 and 14. The angle of unbalance is determinedby turning the-brush holder until the meter reads approximately maximum,then pushing rod 83 inwardly and adjust the brush position closely untilthe meter reads zero. when this adjustment is finished release rod andmeter will show the maximum reading ll iiicative of the magnitude ofunbalance.

The readings for the amount of unbalance and the angle of unbalance aretaken in a similar manner for the right hand and of the rotatable bodyand a detail description is therefore unnecessary.

The body can thus be tested in'two planes of correction, and the propercorrections made to place the body in dynamic balance. The coils 25 ateach end are so connected that the electroe motive force generated iscumulative.

Having thus described my invention what I claim as new and desire tosecure by'Letters Patcut, is:

1. In a balancing machine, means to revolve a body to be tested, meansto translate vibrations, due to unbalanced forces in the body, intoalternating current, a commutator means to which such current isconducted, means to revolve said commutator means at a definite speedrelatively to that of said body, means to reverse the direction of thealternating current at half cycle intervals, a direct current meter,means for electrically connecting said meter with said reversing meansto determine from the value of the reading of the meter the phase angleof unbalance of said body.

2. In a balancing machine, a vibratory support, means to revolve a bodythereon, means responsive to vibrations of said vibratory support tocreate an alternating electromotive force due to unbalanced forces insaid body, a commutator means electrically connected with said force andhaving sets of brushes, with one set circumferentially spaced fromanother set, means to drive said commutator means at a fixed speedrelatively to said body, a direct current meter, and means forelectrically connecting said meter at will of the operator withaselectedset. I m

3. In a balancing machine, a vibratory support, means to revolve a bodythereon, means responsive to vibrations of said vibratory support tocreate an alternating electromotive force due to unbalanced forces insaid body, a commutator means electrically connected with saidelectromotive force and having two sets of brushes, means to drive saidcommutator means at a fixed speed relatively to said body, a directcurrent meter, means for electrically connecting said meter at the willof the operator with one or the other of said sets, and a rotatableangle indicator connected with said brushes to visibly indicate theangle of unbalance.

4. In a balancing machine, a vibratory support, means to revolve a'bodythereon, means responsive to vibrations of said vibratory support tocreate an alternating electromotive force due to unbalanced forces insaid .body, a commutator means electrically connected with saidelectromotive force and having two sets of brushes, means to drive saidcommutator means at a fixed speed relatively to said body, a directcurrent meter, means for electrically connecting said meter at the willof the operator with one or the other of said sets, an angle indicatorfixed to said sets to indicate the .angle of unbalance, and an angleindicating member for said body revolving meansto facilitate the markingofthe angle of unbalance on the body.

5. In a balancing machine, means to generate an alternating current bythe action of unbalanced forces in a revolving body, a commutatorans-4,207

means connected with' such current, contacts insulated from each other,a rotatably adjustable brush holder having sets of brushescircumferentially spaced from each other and cooperating with saidcontacts, an angle indicator fixed to said brush holder, a directcurrent meter and means for electrically connecting said meter with saidbrushes.

8. In a balancing machine, a vibratory support,

means to revolve a body thereon, means responsive to vibrations of saidsupport to create an alternating electromotive force due to unbalancedforces in said body, a commutator means rotatable in synchronism withthe body and electrically connected with said electromotive force, andhaving two sets of brushes positioned at predetermined angles relativelyto each other, a direct current meter, and means to selectively connectsaid meter with one or the other of said sets of brushes.

7. In a balancing machine, a vibratory support, means to revolve a body.thereon, means'responsive to vibrations of said vibratory support tocreate an alternating electromotive force due tounbalanced forces insaid body, a' commutator means electrically connected with said force,and

having sets of brushes, means to change the angular relation of saidcommutator means and said sets of brushes, a direct current meter, andmeans to selectively connect said meter with a selected set of brushes.

8. In a balancing machine, a vibratory support, means to revolve a bodythereon, means to translate vibrations due to unbalanced forces in saidbody into alternating current, means to reverse the direction of thealternating current at half cycle intervals, means to time saidreversing means in relation to the phase angle of said alternatingcurrent, and means to measure the output from said reversing means.

9. In a balancing machine, a vibratory support for a rotatable body tobe tested, means operatively connected with said body to revolve it at aconstant speed, means to translate the vibratory movement of saidsupport into alternating current, means to rectify said alternatingcurrent, and means to measure the current created and thereby indicatethe amount of unbalance said measuring-means also including means. todirectly indicate the angular location of unbalance.

10. In a balancing machine, 'a vibratory support for a body to betested, means operatively relative movement caused by vibratory movementof said support'to thereby create an alternating electric current, meansto integrate said alternating current, and a direct current meter tomeasure the resultant amount of current created and thereby the amountof unbalance of the bodyl 11. In balancing apparatus, means to generateby the action of unbalanced forces in a rotatable body an alternatingelectromotive force which is in proportion to the amplitude of vibrationof the revolving body and the phase relation of which is dependent uponthe location of the unbalance, means to integrate said electromotiveforce and to determine the angular limits of said integration, and meansto measure the integrated current and thereby determine the amount andangular location of unbalance.

BENGT ERIK OHLBON.

